Compared to wireline telephone and public cellular communciation systems, a group call in a Land Mobile Radio (LMR) communciation system is unreliable. That is, a call originator can establish and complete an LMR group call without knowing of the state or participation of other team members, which may have fatal consequences in mission critical communications. For example, a team member's LMR may be temporarily powered down or in shut down state due to a low battery, or the team member may be out of radio frequency range, with the result that the team member may miss the call. Meanwhile, the call originator may not aware that one or more team members have missed some or all information conveyed in the call.
For example, an emerging trend in policing is ‘One-Man Patrolling’ carried out by community public safety officer. Suppose a public safety officer is one-man patrolling a street in a district and enters a building where the officer's LMR is out of service. A command center may not be aware that the officer's LMR is out of service and may originate a group call requesting that all patrolling public safety officers in this district move to a particular site for an emergency event. But the command center may be unaware that the public safety officer has missed this (voice) notification since it is a group call and no voice acknowledgements from individuals are required. Five minutes later, the public safety officer may return to RF coverage and the LMR may automatically return to the LMR commuication network, but the public safety officer is unaware of the missed call.
One of ordinary skill in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of various embodiments of the present invention. Also, common and well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required.